build

# File activerecord/lib/active_record/associations/collection_association.rb, line 142
      def build(attributes = {}, &block)
        if attributes.is_a?(Array)
          attributes.collect { |attr| build(attr, &block) }
        else
          add_to_target(build_record(attributes)) do |record|
            yield(record) if block_given?
          end
        end
      end